Method for making dry sheet-like sample of solid particles from a suspension

ABSTRACT

In a method and apparatus for making a dry sheet-like sample of solid particles from a suspension, a part of the suspension is sampled by a sampling unit as it flows through a pipe or while it is retained in a storage tank, then the sampled suspension is stirred by supplying a compressed air and then dewatered by filtration with vacuum, thereby forming a wet sheet-like intermediate sample of solid particles deposited on a filter. Subsequently, the filter and the intermediate sample deposited thereon are conveyed by an overturning conveyor unit to a drying station while being turned upside down, thereafter intermediate sample is removed from the filter by a sample removing unit, and finally, the wet sheet-like intermediate sample is dried with heat and pressure whereby a dry sheet-like final sample is obtained.

BACKGROUND OF THE INVENTION

The present invention relates to a method and apparatus for making a drysheet-like sample of solid particles from a suspension. It also relatesto a method and apparatus for measuring the pulp concentration of adilute fiber suspension or pulp liquor.

In the paper making industry, control of the pulp concentration is avery important matter to a stable paper-making operation and a uniformquality of paper pulp obtained.

The pulp concentration is a proportion of the oven-dry weight of fibercontents in dilute fiber suspension to the total weight of the dilutefiber suspension which is indicated in terms of weight percent.

According to a conventional practice, the measurement of the pulpconcentration is achieved by first manually sampling a part of thedilute fiber suspension into a measuring cup as it flows through a pipe.Then, the total weight of the sampled dilute fiber suspension ismeasured.

Subsequently, the sampled pulp liquor is squeezed to extract fibercontents which are in turn extended into a wet sheet-like intermediatefiber mat or sample. The intermediate sample is dried by heating withinan oven under appropriate heating conditions such, for example, as at130° C. for 2 hours. Thus, a dry sheet-like final sample or fiber mat isobtained.

The dry final sample is weighed for its oven-dry weight (also known as"absolute dry weight") and a proportion of the oven-dry weight of thedry final sample to the total weight of the dilute fiber suspension iscalculated. The pulp concentration is thus obtained.

The conventional measurement of the pulp concentration substantiallyentirely depends on the manual operation and hence is a time-consumingpractice. Due to the manual operation, the measuring accuracy isrelatively low.

SUMMARY OF THE INVENTION

With the foregoing drawbacks of the prior art in view, it is an objectof the present invention to provide a method and apparatus for making adry sheet-like sample of solid particles from a suspension automaticallyand efficiently.

Another object of the present invention is to provide a method andapparatus for measuring the pulp concentration of a dilute fibersuspension in an automated manner and at a high degree of accuracy.

According to a first aspect of the present invention, there is provideda method of making a dry sheet-like sample of solid particles from asuspension, comprising the steps of: (a) sampling a part of thesuspension as it flows through a pipe or while it is retained in astorage tank; (b) stirring the thus-sampled suspension by supplying acompressed air to the sampled suspension and then dewatering the stirredsuspension by filtration with vacuum, thereby forming a wet sheet-likeintermediate sample of solid particles deposited on a filter; (c)conveying the filter and the wet sheet-like intermediate sampledeposited thereon to a drying station while turning the filter and thewet sheet-like intermediate sample upside down, and subsequentlyremoving the wet sheet-like intermediate sample from the filter; and (d)thereafter, drying the wet sheet-like intermediate sample with heat andpressure, thereby forming a dry sheet-like final sample.

According to a second aspect of the present invention, there is providedan apparatus for making a dry sheet-like sample of solid particles froma suspension, comprising: (a) a sampling unit including a samplingmechanism having a hopper connected in branched fashion to a main pipeor a storage tank for sampling a part of the suspension as it flowsthrough the main pipe or while it is retained in the storage tank, and awater sprinkling mechanism for sprinkling water against the samplingmechanism and an inside surface of the hopper for removing thesuspension adhering to the sampling mechanism and the inside surface ofthe hopper; (b) a wet sheet-like intermediate sample forming unitincluding a tank for holding therein the sampled suspension, a filterremovably disposed in the tank, means for stirring the sampledsuspension held in the tank, and means for dewatering the sampledsuspension from the tank to thereby form a wet sheet-like intermediatesample of solid particles deposited on the filter; (c) an overturningconveyor unit for conveying the filter and the wet sheet-likeintermediate sample from a position within the tank to a drying stationwhile turning the filter and the wet sheet-like intermediate sampleupside down; (d) a sample removing unit for removing the wet sheet-likeintermediate sample from the filter; and (e) a dryer unit disposed atthe drying station and including upper and lower hot plates relativelymovable toward and away from each other to compress the wet sheet-likeintermediate sample therebetween for drying the wet sheet-likeintermediate sample with heat and pressure, thereby forming a drysheet-like final sample.

According to a third aspect of the present invention, there is provideda method of measuring the pulp concentration of a dilute fibersuspension, comprising the steps of: (a) sampling a part of the dilutefiber suspension as it flows through a pipe or while it is retained in astorage tank; (b) stirring the thus-sampled dilute fiber suspension bysupplying a compressed air to the sampled dilute fiber suspension andthen dewatering the stirred dilute fiber suspension by filtration withvacuum, thereby forming a wet sheet-like intermediate sample of solidparticles deposited on a filter; (c) conveying the filter and the wetsheet-like intermediate sample deposited thereon to a drying stationwhile turning the filter and the wet sheet-like intermediate sampleupside down, and subsequently removing the wet sheet-like intermediatesample from the filter; (d) thereafter, drying the wet sheet-likeintermediate sample with heat and pressure, thereby forming a drysheet-like final sample; and (e) transferring the dry sheet-like finalsample to a weighing station and then measuring an oven-dry weight ofthe dry sheet-like final sample for subsequent calculation of the pulpconcentration of the dilute fiber suspension based on the oven-dryweight of the final sample and a total weight of the sampled dilutefiber suspension.

According to a fourth aspect of the present invention, there is providedan apparatus for measuring the pulp concentration of a dilute fibersuspension, comprising: (a) a sampling unit including a samplingmechanism having a hopper connected in branched fashion to a main pipeor a storage tank for sampling a part of the dilute fiber suspension asit flows through the main pipe or while it is retained in the storagetank, and a water sprinkling mechanism for sprinkling water against thesampling mechanism and an inside surface of the hopper for removing thedilute fiber suspension adhering to the sampling mechanism and theinside surface of the hopper; (b) a wet sheet-like intermediate sampleforming unit including a tank for holding therein the sampled dilutefiber suspension, a filter removably disposed in the tank, means forstirring the sampled dilute fiber suspension held in the tank, and meansfor dewatering the sampled dilute fiber suspension from the tank tothereby form a wet sheet-like intermediate sample of solid particlesdeposited on the filter; (c) an overturning conveyor unit for conveyingthe filter and the wet sheet-like intermediate sample from a positionwithin the tank to a drying station while turning the filter and the wetsheet-like intermediate sample upside down; (d) a sample removing unitfor removing the wet sheet-like intermediate sample from the filter; (e)a dryer unit disposed at the drying station and including upper andlower hot plates relatively movable toward and away from each other tocompress the wet sheet-like intermediate sample therebetween for dryingthe wet sheet-like intermediate sample with heat and pressure, therebyforming a dry sheet-like final sample; (f) a final sample transfer unitfor transferring the dry sheet-like final sample from the dryer unit toa weighing station; and (g) a weighing unit disposed at the weighingstation for measuring an oven-dry weight of the final sample.

The above and other objects, features and advantages of the presentinvention will become more apparent from the following description whenmaking reference to the detailed description and the accompanying sheetsof drawings in which preferred structural embodiments incorporating theprinciples of the present invention are shown by way of illustrativeexample.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing the sequence of processing stepsachieved in a method of making a dry sheet-like sample of solidparticles from a suspension according to the present invention;

FIG. 2 is a block diagram showing the sequence of processing stepsachieved in a method of measuring the pulp concentration of a dilutefiber suspension;

FIG. 3 is a front elevational view of an apparatus for measuring thepulp concentration of a dilute fiber suspension according to the presentinvention;

FIG. 4 is a cross-sectional view taken along line IV--IV of FIG. 3;

FIG. 5 is a view taken in the direction of the arrows along the lineV--V of FIG. 3;

FIG. 6 is a view taken in the direction f the arrows along the lineVI--VI of FIG. 3;

FIG. 7 is a fragmentary cross-sectional view of a sampling unit withparts broken away for clarity;

FIG. 8 is an enlarged perspective view of the sampling unit with partsbroken away for clarity;

FIG. 9 is a cross-sectional view of a modified sampling unit;

FIG. 10 is a view similar to FIG. 9, but showing another sampling unit;

FIG. 11 is a perspective view of a wet sheet-like intermediate sampleforming unit, with parts broken away for clarity, illustrating the unitin the stirring mode;

FIG. 12 is a view similar to FIG. 11, but showing the wet sheet-likeintermediate sample forming unit in the dewatering mode;

FIG. 13 is a plan view of a part of an overturning conveyor unit havinga filter shown with parts broken away for clarity and a wet sampleremoving unit associated with the filter;

FIG. 14 is a front elevational, partly cross-sectional view illustratingthe operation of the overturning conveyor unit;

FIGS. 15A and 15B are perspective views illustrative of the operation ofa hot press having a cooperating pair of hot plates;

FIG. 16 is a perspective view showing a weighing unit and a dry sampletransfer unit associated therewith;

FIGS. 17 and 18 are views similar to FIGS. 11 and 12, respectively, butshowing a modified wet sheet-like intermediate sample forming unit;

FIGS. 19, 20 and 21 are perspective views showing the operation of amodified sample removing unit; and

FIG. 22 is a perspective view of a dry sample transfer unit according toanother embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings wherein like reference charactersdesignate like or corresponding parts throughout the several views, andmore particularly to FIG. 3, there is shown a pulp concentrationmeasuring apparatus embodying the present invention.

The pulp concentration measuring apparatus includes a substantiallyrectangular frame 1 having an upper portion on which a sampling deviceor unit 3 is mounted for sampling a predetermined quantity of dilutefiber suspension.

The frame 1 further has a horizontal table 5 disposed in a substantiallyintermediate position as viewed in the vertical direction. The table 5supports thereon a wet sheet-like intermediate sample forming device orunit 7 incorporating a stirring means and a dewatering means, anoverturning conveyor device or unit 9 for transferring the wetintermediate sample while turning the same upside down, a sampleremoving device or unit 10 associated with the overturning conveyor unit9 for removing the wet sheet-like intermediate sample from a filter, adryer device or unit 11 for drying the wet sheet-like intermediatesample with heat and pressure, thereby forming a dry sheet-like finalsample, a transfer device or unit 12 for transferring the dry sheet-likefinal sample to a weighing station, and a weighing device or unit 16 forweighing an oven-dry weight of the dry sheet-like final sample at theweighing station.

The dilute fiber suspension collected by the sampling unit 3 is suppliedto the wet sheet-like intermediate sample forming unit 7 where a wetsheet-like intermediate sample 13 of fibrous materials is formed. Thethus-formed wet sheet-like intermediate sample 13 is transferred by theoverturning conveyor unit 9 to the dryer unit 11 at which it is removedfrom a filter by the sample removing unit 10.

Then, the wet sheet-like intermediate sample 13 is dried with heat andpressure by the dryer unit 11. A dry sheet-like final sample 14 is thusobtained. The final sample 14 is transferred by the transfer unit 12 toa weighing position where it undergoes subsequent measurement of itsoven-dry weight. A proportion of the oven-dry weight of the final sample14 to the total weight of the sampled dilute fiber suspension iscalculated to obtain the pulp concentration of the dilute fibersuspension.

The construction of the respective units will be described below ingreater detail.

The wet sheet-like intermediate sample forming unit 7 includes, as shownin FIGS. 3 and 11, a filter 15 movably disposed over a circular openingin the table 3, and a stirring tank 17 disposed on the filter 15.

The filter 15 is composed of a circular fine wire net having anappropriate size, such as 100 mesh which is small enough to separatefiber contents from water, thereby forming a deposit of fiber contentson the filter 15 when the sampled dilute fiber suspension is poured outinto the stirring tank 17. The shape and configuration and the materialof the filter 15 are not limited to those shown in the illustratedembodiment.

The stirring tank 17 is in the form of a hollow cylinder and isdetachably and sealingly fitted over an outer peripheral edge of thecircular filter 15. The stirring tank 17 is connected to an operatingarm 22 of a rotary actuator 21. The rotary actuator 21 is driven to movethe stirring tank 17 between a vertical operating position in which thestirring tank 17 is fitted over the filter 15 as indicated by the solidlines in FIG. 3, and a tilted waiting position in which the stirringtank 17 is detached from the filter 15 as indicated by the phantom linesin the same figure. The stirring tank 17 is disposed in the tiltedwaiting position when a wet sheet-like intermediate sample 13 formed onthe filter 15 is removed from the filter 15.

A cup-shaped suction tank 23 is disposed directly below the filter 15and operatively connected with a vacuum pump 23 and an air compressor 26that are disposed below the suction tank 23.

The suction tank 23 and the vacuum pump 25 are connected by a pipe 27via a shutoff valve 28. The pipe 27 has an end connected to the bottomof the suction tank 23. The air compressor 26 has an air supply pipe 29from which a small air supply pipe 31 is branched. The branched airsupply pipe 31 is connected to the pipe 27 adjacent to the end thereofconnected to the suction tank 23. The branched air supply pipe 31 has ashutoff valve 35.

When the sampled dilute fiber suspension poured out into the stirringtank 17 is to be stirred, the air compressor 26 is driven to supply acompressed air to the interior of the stirring tank 17 successivelythrough the pipe 29, the pipe 31 and the pipe 27. When the stirring ofthe sampled dilute fiber suspension is completed, water in the dilutefiber suspension is drawn by filtration with vacuum. In this instance,the vacuum pump 25 is driven to withdraw the water from the suction tank23 and the stirring tank 17 through the pipe 27. During that time, theoperation of the air compressor 27 is interrupted. After completion ofthe vacuum dewatering, the air compressor 26 is driven again to supply acompressor air to the suction tank 23, the filter 15 and the stirringtank 17. The suction tank 23, the filter 15 and the stirring tank 17restore their initial conditions.

The sample removing unit 10 is constructed as described below.

The air supply pipe 29 has another branched air supply pipe 33 acrosswhich a shutoff valve 37 is disposed. An air supply pipe in the form ofa crisscross pipe 36 (FIG. 13) is disposed below the filter 15 andconnected to a flexible air pipe 38 which in turn is connected to thebranched air supply pipe 33 via a nozzle 39 formed in a peripheral wallof the suction tank 23. The crisscross air supply pipe 36 has aplurality of uniformly spaced air nozzles 40 facing upwardly so that acompressed air supplied through the air supply pipes 29, 33 and 38 tothe crisscross air supply pipe 36 is ejected from the air nozzles 40onto the underside of the wet sheet-like intermediate sample 13, therebyremoving the intermediate sample 13 from the filter 15. Since the airnozzles 40 are spaced at substantially equal intervals, the compressedair is distributed uniformly over the surface of the wet intermediatesample 13. As a result, removal of the wet intermediate sample 13 can beeffected smoothly without damaging the intermediate sample 13.

The removal of the intermediate sample 13 is achieved in subsequent tothe overturning conveyance of the intermediate sample 13 by means of theoverturning conveyor unit 9.

The overturning conveyor unit 9 includes a rotary actuator 43 disposedbetween the intermediate sample forming unit 7 and the dryer unit 11 andhaving an actuating arm 45 connected to the filter 15.

The rotary actuator 43 is driven to angularly move or turn the actuatingarm 45 and the filter 15 concurrently about the axis of the actuatingarm 45 through an angle of 180 degrees, so that the intermediate sample13 formed on the filter 15 is conveyed from a stirring and suctionstation to a drying station. The intermediate sample 13, as it istransferred to the drying station, is inverted or turned upside down.The overturning conveyor unit 9 thus constructed is simple inconstruction and small in size and hence occupies only a small space forinstallation.

The dryer unit 11 comprises a hot press disposed at the drying station.The hot press is composed of an upper hot plate 47 fixedly mounted abovethe table 5, and a lower hot plate 49 disposed on the table 5 forsupporting thereon the wet sheet-like intermediate sample.

The lower hot plate 49 is connected to a piston rod 53 of a shiftcylinder 51. When the shift cylinder 51 is actuated to extend the pistonrod 53, the lower hot plate 49 is moved upwardly toward the stationaryupper hot plate 47 while the wet sheet-like intermediate sample 13 isheld on the lower hot plate 49 so that the wet intermediate sample 13 iscompressed by and between the upper and lower hot plates 47, 49.

Each of the upper and lower hot plates 47, 49 has an induction heater11a, 11b (FIGS. 15A and 15B) incorporated therein and including aninduction coil connected to an electric power supply (not shown) forheating the hot plate 47, 49. The temperature of the respective hotplates 47, 49 is controlled by thermostat. The induction heater 11a, 11bmay be incorporated in at least one of the upper and lower hot plates47, 49.

In the illustrated embodiment, the dryer unit 11 employs an inductionheating system. When energized, the induction coil produces anelectromagnetic flux. The electromagnetic flux, as it passes throughmetal plates attached to end edges of the hot plate 47, 49, is convertedinto eddy-current induced in the metal plates. Then the metal platesgenerate heat, thereby heating the hot plates 47, 49 and the wetsheet-like intermediate sample 13 compressed between the upper and lowerhot plates 47, 49. The wet intermediate sample 13 is thus dried withheat and pressure. The induction heating system may be replaced by amicrowave heating system or an electric heating system.

As shown in FIGS. 15A and 15B, the upper surface of the lower hot plate49 has a plurality of parallel spaced grooves 50. The grooves 50 permitwater vapor to escape through the grooves 50 to the outside of the hotpress while the wet intermediate sample 13 is being heated. With thegrooves 50 thus provided, the heating efficiency is increased and thenecessary heating time is reduced. The upper hot plate 47 may havesimilar grooves. The number, size and configuration of the grooves 50are not limited to those of the illustrated embodiment. Furthermore, theupper hot plate 47 may be vertically movable in which instance the lowerhot plate 49 is stationary and the shift cylinder 51 is connected to theupper hot plate 47 for reciprocating the same with respect to thestationary lower hot plate 49, as shown in FIG. 21.

As best shown in FIGS. 3 and 16, the transfer unit 12 is disposedadjacent to the lower hot plate 49 for feeding a dry sheet-like finalsample 14 from the dryer unit 11 onto the weighing unit 16 via a chute55. The chute 55 is disposed adjacent to the downstream end of the lowerhot plate 49.

The weighing unit 16 includes an electronic weighing scale 57 mounted ona bracket 56 attached to the frame 1 (FIG. 3). The transfer unit 12, asshown in FIG. 16, includes a rotary actuator 58 having an actuating arm59 pivotally movable in a horizontal plane lying immediately above theupper surface of the lower hot plate 49 so that the final sample 14 isdisplaced from the lower hot plate 49 onto the chute 55. Subsequently,the final sample 14 falls down along the chute 55 onto the electronicweighing scale 57 of the weighing unit 16.

The sampling unit 3 will be described below in greater detail withreference to FIGS. 6, 7 and 8.

The pulp liquor to be measured for its pulp concentration flows througha main pipe 61. The main pipe 61 has a branched pipe 63 to which ahopper 65 is connected. The hopper 65 has at its lower end a dischargehole 67 disposed adjacent to an upper end of the stirring tank 16 whenthe stirring tank 16 is disposed in its vertical operating position. Themain pipe 61 may be replaced with a storage tank in which a dilute fibersuspension is retained.

As shown in FIGS. 7 and 8, the hopper 65 houses therein a samplingmechanism 69 which includes a pair of parallel spaced circular plates71, 73 connected together by means of a horizontal shaft 75. Thecircular plates 71, 73 have a same outside diameter which is slightlysmaller than the inside diameter of the branched pipe 63 so that thecircular plates 71, 73 are slidably movable along the branched pipe 63.

A shift cylinder 77 (FIG. 7) is disposed on the outside of the hopper 65and has a piston rod 79 extending into the internal space of the hopper65 and connected concentrically to the horizontal shaft 75.

When the shift cylinder 77 is actuated to reciprocate the shaft 75 viaits piston rod 79, the plates 71, 73 are movable between the main pipe61 and the hopper 65. With this reciprocating movement of the plates 71,73, a part of the dilute fiber suspension is trapped between the plates71, 73 and collected into the hopper 65. The collected dilute fibersuspension is thereafter poured out into the stirring tank 17.

The quantity of the collected or sampled dilute fiber suspension isdetermined depending on the space between the two plates 71, 73 so thata desired quantity of dilute fiber suspension can be collected byproperly adjusting the spacing between the plates 71, 73.

The sampling mechanism 69 is associated with a water sprinklingmechanism 81 disposed on the upper end of the hopper 65. The watersprinkling mechanism 81 includes a water supply pipe 83 and a pair ofwater sprinkling nozzles 85, 87 branched from the water supply pipe 83and disposed within the hopper 65.

With the water sprinkling mechanism 81 thus constructed, water issprinkled over the inside surface of the hopper 65 and the outsidesurfaces of the moving parts 71, 73, 75 of the sampling mechanism 69,thereby washing away or removing the dilute fiber suspension adhering tothe hopper 65 and the moving parts 71, 73, 75. The removed dilute fibersuspension is discharged from the hopper 65 through the discharge hole67 and loaded into the stirring tank 17.

As shown in FIG. 3 and 11, a level sensor 89 is disposed within thestirring tank 17 for detecting the level of the dilute fiber suspensionretained in the stirring tank 17 to thereby control on-off operation ofthe sprinkling mechanism 81 in such a manner to prevent overflow of thedilute fiber suspension.

The pulp concentration measuring apparatus of the foregoing constructionoperates as follows.

The operation begins from a sampling step as designated by "a" in FIG.2.

In the sampling step "a", the shift cylinder 77 (FIG. 7) is actuated toreciprocate the shaft 75, thereby moving the plates 71, 73 into and outof the main pipe 61 whereupon a predetermined quantity of dilute fibersuspension is sampled into the hopper 65. The sampled dilute fibersuspension is supplied from the discharge hole 67 into the stirring tank17. During that time, the water sprinkling mechanism 81 is driven tosprinkle water into hopper 65. With this water sprinkling, the dilutefiber suspension adhering to the outer surfaces of the plates 71, 73 andthe shaft 75 and also on the inside surface of the hopper 65 is washedaway and falls into the stirring tank 17 together with the sprinkledwater.

When a dilute fiber suspension loaded in the stirring tank 17 reaches apredetermined level, the level sensor 89 issues a command signal tointerrupt sprinkling operation of the water sprinkling mechanism 81.

Then the operation proceeds to a wet sheet-like intermediate sampleforming step as designated by "b" in FIG. 2.

At the beginning of the intermediate sample forming step "b", the pulpliquor fills the internal space of the stirring tank 17 and the internalspace of the suction tank 23 disposed below the stirring tank 17 withthe filter 15 disposed between the tanks 17 and 23.

Then, a compressed air produced by the air compressor 26 is suppliedthrough the pipes 29, 31, 27 into the suction tank 23 and the stirringtank 17 across the filter 15, as shown in FIG. 11. Consequently, thedilute fiber suspension is uniformly stirred by the compressed air andhence fiber contents are uniformly dispersed in water.

Thereafter, the vacuum pump 25 is energized to draw the water contentsin the dilute fiber suspension through the pipe 27. With this vacuumdewatering, the water contents are completely removed from the tanks 17,23 while fiber contents are deposited uniformly over an upper surface ofthe filter 15, as shown in FIG. 12. The fiber contents thus depositedform a sheet-like intermediate sample 13 having a substantially uniformthickness. The intermediate sample 13 is dewatered to a certain extentbut still wet.

Then, the vacuum pump 25 is de-energized and the compressed air issupplied again from the air compressor 26 to the suction tank 23 and thestirring tank 17 to release the vacuum state in the tanks 17, 23.

The foregoing intermediate sample forming step "b" is followed by anoverturning conveyance step "c" such as designated by "c" in FIG. 2.

In the overturning conveyance step "c", the stirring tank 17 isretracted into a tilted waiting position as indicated by the phantomlines in FIG. 3. Then, the rotary actuator 43 is driven to pivot theactuating arm 45 about its proximal end through an angle of 180 degrees,thereby causing the filter 15 to turn through an angle of 180 degrees.With this angular movement of the filter 15, the wet sheet-likeintermediate sample 13 is turned upside down and transferred to thelower hot plate 49 of the dryer unit 11, as shown in FIG. 14. Since thefilter 15 is turned upside down, the intermediate sample 13 is held indirect contact with the upper surface of the lower hot plate 49.

A sample removing step as designated by "d" in FIG. 2 follows theoverturning conveyance step "c" described above.

In the sample removing step "d", a compressed air is suppledsuccessively through the pipe 29, the pipe 33, the nozzle 39, and theflexible pipe 38 to the crisscross pipe 36 and then ejected downwardlyfrom the nozzles 40 against the upper surface of the intermediate sample13. With this compressed air thus supplied, the intermediate sample 13is removed from the filter 15.

The rotary actuator 43 is driven again to return the filter 15 to itsinitial position.

The foregoing sample removing step "d" is followed by a drying stepdesignated by "e" in FIG. 2.

In the drying step "e", the shift cylinder 51 is actuated to move thelower hot plate 49 toward the stationary upper hot plate 47 while thesheet-like intermediate sample 13 is supported on the lower hot plate49.

Thus, the wet sheet-like intermediate sample 13 is sandwiched betweenthe upper and lower hot plates 47, 49, as shown in FIG. 15B. The wetintermediate sample 13 is dried by heating with the hot plates 47, 49.During that time, water vapor is allowed to escape through the grooves50 and, therefore, the heating efficiency is substantially improved andthe necessary heating time can be reduced.

The wet intermediate sample is compressed by the upper and lower hotplates 47, 49 at a pressure of 5 kg/cm², for example. The upper andlower hot plates 47, 49 are heated at about 140° C.

When a predetermined heating time period elapses, the lower hot plate 49is lowered to its initial position.

Then the operation proceeds to a transfer and weighing step such asdesignated by "f" in FIG. 2.

In the transfer and weighing step "f", the rotary actuator 58 is drivento turn the actuating arm 59 from the solid-lined position to thephantom-lined position, thereby forcing a dry sheet-like final sample 14from the lower hot plate 49 toward the chute 55. Then, the final sample14 slides down along the chute 55 and falls onto the electronic weighingscale 57 of the weighing unit 12, as shown in FIG. 16. The weighingscale 57 measures an oven-dry weight of the dry final sample 14. Thethus-measured oven-dry weight and a previously measured total weight ofthe sampled dilute fiber suspension are used to calculate the pulpconcentration of the dilute fiber suspension.

As described above, the apparatus of the present invention is capable ofmeasuring the pulp concentration automatically. Such automatic pulpconcentration measurement obviates the need for laborious manualoperation and requires only a short period of measuring time.

The present invention is not limited to the foregoing embodiment and itis also useful when embodied in a method of making a dry sheet-likesample of solid particles from a suspension, such as shown in FIG. 1.The dry sample making method shown in FIG. 1 includes a series ofprocessing steps A-E which are substantially the same as those "a"-"e"of the pulp concentration measuring method shown in FIG. 2 with theexception that the transfer and weighing step "f" is no longer necessaryin the dry sample making method shown in FIG. 1. The dry sample may beused for a measurement of ash content in which the dry sample undergoessubsequent burning, a color analysis of fiber contents, and variousmeasurements and analyses other than specified above.

FIG. 9 shows a modified form of the sampling unit. The modified samplingunit includes a sampling mechanism in the form of a screw pump. Thescrew pump includes a shaft 95 having a helical screw blade 93 androtatably received in a branched pipe 91 extending between the main pipe61 and the hopper 65. The shaft 95 is coupled with a drive motor 97disposed on the outside of the hopper 65.

FIG. 10 illustrates another modified sampling unit which employs anaxial flow pump. The axial flow pump sampling unit includes an impeller103 rotatably disposed in a branched pipe 101 extending from the mainpipe 61 to the hopper 65, and a drive motor 105 connected to theimpeller 103 for rotating the same.

Other sampling units replaceable with any of the sampling unitsspecified above include a screw conveyor and a suction sampling unit.

FIGS. 17 and 18 show a modified wet intermediate sample forming unit 7'according to the invention. The modified sample forming unit 7' differsfrom the sample forming unit 7 of the foregoing embodiment shown inFIGS. 11 and 12 in that the branched air supply pipe 31 is directlyconnected to the bottom of the suction tank 23.

FIGS. 19 through 21 illustrate a modified sample removing unit 10' whichcomprises a rotary actuator 107 having a drive shaft 109, and anelongate nozzle 111 connected to the drive shaft 109. In response to theoperation of the rotary actuator 107, the nozzle 111 is angularlymovable between a vertical waiting position (FIGS. 19 and 21) remotefrom the dryer unit 11, and a tilted operating position (FIG. 20)adjacent to the upper side of the filter 15 as the filter 15 is disposedon the lower hot plate 49. When the nozzle 111 is disposed in itsoperating position shown in FIG. 20, a compressed air supplied from theair compressor 26 (FIG. 3) is ejected from the nozzle 111 against theupper side of the filter 15, thereby removing a wet intermediate sample13 (FIG. 21) from the filter 15.

A modified dry sample transfer unit 12' shown in FIG. 22 differs fromthe dry sample transfer unit 12 shown in 16 in that a transverse pusherbar 113 connected to a piston rod 115 of a shift cylinder 117reciprocates along the upper surface of the lower hot plate 49 inresponse to the operation of the shift cylinder 117 so that a dry finalsample 14 is transferred from the dryer unit 11 to an electronicweighing scale 57 of the weighing unit 16 disposed adjacent to the lowerhot plate 49.

Obviously various minor changes and modifications of the presentinvention are possible in the light of the above teaching. It istherefore to be understood that within the scope of the appended climesthe invention may be practiced otherwise than as specifically described.

What is claimed is:
 1. A method of making a dry sheet-like sample ofsolid particles from a suspension, comprising the steps of:(a) samplinga part of the suspension as it flows through a pipe or while it isretained in a storage tank (b) stirring the thus-sampled suspension bysupplying compressed air to the sampled suspension and then dewateringthe stirred suspension on a filter by filtration with vacuum, therebyforming a wet sheet-like intermediate sample of solid particlesdeposited on the filter; (c) conveying the filter and the wet sheet-likeintermediate sample deposited thereon to a drying station comprising anupper hot plate and a lower hot plate movable toward and away from eachother, while turning the filter and the wet sheet-like intermediatesample upside down onto the lower hot plate of the drying station, andsubsequently removing the wet sheet-like intermediate sample from thefilter; and (d) thereafter, drying the wet sheet-like intermediatesample with heat and pressure in the drying station, thereby forming adry sheet-like final sample.